1. Field of the Invention
The present invention relates to a method for determining a kind of optical recording medium.
2. Description of the Related Art
FIG. 1 is a view of a configuration of a servo system of a related art optical disc device.
The optical disc device includes an LD driver 10, an I/V amplifier, an RF amplifier 30, a spindle motor 40, a spindle driver 50, a sled motor 60, a focus-tracking slid drive 70, and a digital servo processor 80.
Referring to FIG. 1, an object lens of an optical pick-up performs a focus servo operation for reading data in a vertical direction and a tracking servo operation for reading data in a horizontal direction, and reads the data by following a track of an optical disc by the focus-tracking slid driver 70.
In this case, before the data of the optical disc is read by following the track thereof, a kind of inserted optical disc should be recognized first. This is because the data of the optical disc can be accurately read only upon recognizing the kind of the inserted optical disc because of varying distances between an optical disc surface and a data-recording surface and between data and data according to kinds of optical discs. The distance between data is referred to as a track pitch.
FIGS. 2 and 3 are views for describing the related art method for determining a kind of optical disc. In the related art method, a distance between a surface and a data recording surface of an optical disc 10 is used to determine the kind of optical disc 10.
Referring to FIGS. 2 and 3, a laser is turned on and a lens 20 is vertically lifted up. Then, focus searching is performed with the lens 20 moved down to thereby obtain a time difference between a focus boundary waveform, which is a signal reflected from the surface of the optical disc 10, and a focus boundary waveform, which is a signal reflected from the data recording surface thereof. Accordingly, it can be determined whether the inserted optical disc is a DVD or a CD.
A distance (t2) between an optical disc surface and a data recording surface of a CD is twice greater than that (t1) between an optical disc surface and a data recording surface of a DVD. For this reason, the time interval between the focus boundary waveform from an optical disc surface and the focus boundary waveform from an optical disc data recording surface is twice longer than that of the DVD.
When a reference time interval of an optical disc is set in such a manner, the time interval of an inserted optical disc may be compared to the reference time interval to thereby obtain a distance corresponding to the time interval between waveforms of the inserted optical disc. Accordingly, the kind of inserted optical disc may be determined.
However, the related art method for determining the kind of optical disc is problematic for the following reason. The determination is only possible for optical discs with different distances between optical disc surfaces and data recording surfaces thereof. If different kinds of optical discs have the same distances between the optical disc surfaces and the data-recording surfaces, distinguishment between the two cannot be made. For example, both current HD-DVD and DVD have the same distance of 0.6 mm between the optical disc surfaces and the data recording surfaces, and the related art method cannot distinguish between the HD-DVD and DVD.